This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-015285, filed Jan. 24, 2001; and No. 2001-238216, filed Aug. 6, 2001, the entire contents of both which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a by-product elimination device used in a power supply system, and more particularly to a by-product elimination device used in a portable power supply system with a high energy utilization efficiency.
2. Description of the Related Art
In all household and industrial fields, various kinds of chemical cells are used. For example, a primary cell such as an alkaline dry cell or a manganese dry cell is often used in watches, cameras, toys, and portable acoustic devices, and it has a characteristic that its quantity of production is large from the global viewpoint and it is inexpensive and readily available.
A secondary cell such as a lead storage battery, a nickel-cadmium storage battery, a nickel-hydrogen storage battery, a lithium ion battery is often used in mobile phones or personal digital assistances (PDA) which are in widespread use in recent portable devices such as a digital video camera or a digital still camera, and it has a characteristic which is superior in the economical efficiency because it can be repeatedly charged and discharged. Among secondary cells, the lead storage battery is utilized as a start-up power supply for vehicles or marine vessels or an emergency power supply in industrial facilities or medical facilities and the like.
In recent years, with the rising interest in environmental concerns or energy problems, problems concerning waste materials generated after use of chemical cells such as described above or those concerning the energy conversion efficiency have come under close scrutiny.
The primary cell has its inexpensive product price and is readily available as described above, and there are many devices which utilize this cell as a power supply. Further, basically, when the primary cell is once discharged, the battery capacity can not be recovered, namely, it can be used only once (which is a so-called disposable battery). A quantity of waste materials per year, therefore, exceeds, several millions tons. Here, there is static information mentioning that a ratio of the entire chemical cells which are collected for recycling is only approximately 20% and remaining approximately 80% is thrown away in the natural world or subjected to landfill disposal. Thus, there is fear of environmental destruction and disfigurement of the natural environment by heavy metal such as mercury or indium included in such uncollected batteries.
Verifying the above-described chemical battery in the light of the efficiency of use of an energy resource, since the primary cell is produced by utilizing the energy which is approximately 300-fold of the dischargeable energy, the efficiency of use of the energy is less than 1%. Even in case of the secondary cell which can be repeatedly charged and discharged and is superior in the economical efficiency, when the secondary cell is charged from a domestic power supply (convenience outlet) or the like, the efficiency of use of the energy drops to approximately 12% due to the efficiency of power generation in an electric power plant or the transmission loss. Therefore, it can not be said that the energy resource is necessarily efficiency utilized.
Thus, the attention is recently drawn on various kinds of new power supply systems or power generation systems (which will be generically referred to as a xe2x80x9cpower supply systemxe2x80x9d hereinafter) including a fuel battery which has less influence (burden) on the environment and is capable of realizing the extremely high energy utilization efficiency of, e.g., approximately 30 to 40%. Furthermore, for the purpose of application to a drive power supply for vehicles or a power supply system for business use, a cogeneration system for domestic use and others, or substitution for the above-described chemical cell, study and development for practical application are carried out extensively.
However, there are various problems to make the power generation element with the high energy utilization efficiency of the fuel cell or the like smaller and lighter, and apply it as the portable or carry-along power supply system, for example as the alternate for the chemical cell above described, hereafter.
Actually, in the power supply system that effuses hydrogen from an alloy which occludes hydrogen and generates electric power by hydrogen, there is a problem that power generation capacity (power consistency) or energy per unit volume of the hydrogen occludent alloy is low. Also, there is a problem that the power consistency and output grade are low in the previous fuel direct power generation system which supplies an organic chemistry fuel to the fuel cell directly.
On one hand, the fuel reforming power generation system supplies hydrogen to the fuel cell from the fuel reformer which forms hydrogen from the organic chemistry fuel, for example methanol or methane gas. The fuel reforming power generation system has such an advantage that energy amount per unit capacity of the fuel vessel is high in comparison with the fuel direct power generation system or said hydrogen occludent alloy power generation system. Here, in the fuel reforming power generation system that combines said vapor fuel reformer with the oxygen-hydrogen fuel cell, by-product such as carbon dioxide gas is generated in addition to the hydrogen gas. There is also a problem that the power generation efficiency declines, since the concentration of the hydrogen gas which contributes to power generation is low in case that mixed gas based on the hydrogen gas and carbon dioxide gas is simply supplied to the fuel cell. Further, there is a problem that virulent carbon monoxide may be contained slightly in the mixed gas.
Furthermore, due to the volume of the vapor fuel reformer itself, the power generation system known in the prior art could not obtain the power consistency sufficient to use as the portable or carry-along power supply system.
Then, the present invention has an advantage to obtain sufficient power consistency and energy utilization efficiency at an easy rate without exhaust of by-product to outside as possible.
A by-product elimination device used in a power generation system according to one aspect of the present invention, comprises at least any one of:
(a) a fuel pack provided with a fuel charged portion having a power generation fuel having a liquid or gas containing hydrogen charged therein; and
(b) a power generation module which can be attached to or detached from the fuel pack, the module including a reforming portion which transforms the power generation fuel supplied from the fuel charged portion into first gas containing hydrogen gas and carbon dioxide as main components, and a fuel cell which generates an electrical energy by using the hydrogen gas contained in the first gas,
the by-product elimination device further comprising an absorbent charged portion which selectively absorbs carbon dioxide contained in the first gas fed from the reforming portion and feeds second gas whose carbon dioxide concentration is lowered by the first gas to the fuel cell.
That is, in the by-product elimination device, the power generation fuel including hydrogen element charged in the fuel charged portion is transformed to the hydrogen (H2)-carbon dioxide (CO2) mixed gas (first gas) by the reforming portion firstly. The first gas is transformed to the second gas based on hydrogen gas by absorbing and eliminating carbon dioxide gas by the absorbent charged portion. The second gas is supplied to the hydrogen-oxygen fuel cell (fuel cell). The second gas has high hydrogen gas concentration for power generation, thereby improving the power generation efficiency of the fuel cell highly in comparison with the case that the power generation element don""t comprise the absorbent charged portion. As a result, it is possible to apply the fuel cell as the portable or carry-along power supply system that has high energy utilization efficiency and high power consistency and can be controlled easily.
A fuel pack used in the power supply system according to the other aspect of the present invention comprises:
a fuel charged portion which can be connected to the fuel pack, and contains a fuel to be supplied to a reforming portion which generates hydrogen and carbon dioxide from the fuel, and whose volumetric capacity is reduced as carbon dioxide is generated in the reforming portion; and
a carbon dioxide absorption portion which absorbs carbon dioxide generated in the reforming portion and whose volumetric capacity is increased as carbon dioxide is generated in the reforming portion.
The carbon dioxide absorption portion expands when it absorbs carbon dioxide to supply hydrogen with high concentration to the fuel cell. In the fuel charged portion, however, whose volumetric capacity is reduced as carbon dioxide is generated in the reforming portion, whereby there is no need to make the fuel pack large. As a result, the portable power generation system can be obtained.
A fuel pack used in the power supply system according to further aspect of the present invention, comprises:
a fuel charged portion which contains a fuel to be supplied to a reforming portion which generates mixed gas containing hydrogen and a first by-product from the fuel, and whose volumetric capacity is reduced as the first by-product is generated in the reforming portion;
a first by-product absorption portion which generates a second by-product by absorbing the first by-product from the mixed gas, and whose volumetric capacity is increased as the first by-product is generated in the reforming portion; and
a second by-product absorption portion which absorbs hydrogen fed from the reforming portion and the second by-product fed from the first by-product absorption portion.
The first by-product absorption portion and the second by-product absorption portion absorb the first by-product and the second by-product respectively, thereby supplying hydrogen with high concentration to the fuel cell.
A fuel pack used in the power supply system according to further aspect of the present invention comprises:
a fuel charged portion which contains a fuel to be supplied to a reforming portion which generates mixed gas including hydrogen and a first by-product from the fuel, and whose volumetric capacity is reduced as the first by-product is generated in the reforming portion;
a first by-product absorption portion which absorbs the first by-product from the mixed gas, and whose volumetric capacity is increased as the first by-product is generated in the reforming portion; and
a second by-product absorption portion which collects a second by-product from a fuel cell which generates power by using hydrogen fed from the first by-product and also generates the second by-product, and whose volumetric capacity is increased as power is generated in the fuel cell.
Consequently, the by-products that are formed until the power generation is performed can be accommodated therein. As result, the effect on environment at the time of the power generation can be controlled, and hydrogen with high concentration may be supplied to the fuel cell, thereby performing the power generation effectually.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.